Laminated safety glass

ABSTRACT

A composition for an interlayer film of a laminated safety glass, said composition comprising (A) a thermoplastic resin resulting from copolymerization of (1) vinyl chloride, (2) glycidyl methacrylate and (3) at least one monomer selected from the group consisting of ethylenic hydrocarbons, vinyl esters of fatty acids, acrylic esters and vinyl ethers, and (B) a plasticizer.

This application is a division of Ser. No. 155,082, filed June 2, 1980now abandoned.

FIELD OF THE INVENTION

This invention relates to an interlayer of a laminated safety glass.More specifically, it provides an interlayer for laminated safetyglasses which has superior penetration resistance, good handleability inbonding, and high bond strength.

BACKGROUND OF THE INVENTION

It has been widely known to use a film of plasticized polyvinyl butyralas an interlayer for bonding the individual glass sheets of a laminatedsafety glass. The plasticized polyvinyl butyral film is widely used insafety glass in automobiles, air planes and building materials becauseof its high adhesiveness and superior light stability, transparency andlow-temperature flexibility.

The surface of the plasticized polyvinyl butyral film, however, is verytacky, and presents a problem of blocking at the time of windup afterfilm formation. It is the current practice to prevent blocking byembossing the surface of the film, or spraying an antiblocking agentsuch as sodium hydrogen carbonate on the surface of the film. However,this brings about the defect that when glasses are to be bonded throughthe polyvinyl butyral film, the film must go through the steps ofwashing and drying for removal of the antiblocking agent before use.

Use of a plasticized polyvinyl chloride film is effective for preventingblocking of the interlayer film. But since this film is not adhesive toglass, it is useless as an interlayer of laminated safety glass.

It is known to use a film of a vinyl chloride/glycidyl methacrylatecopolymer containing about 40% by weight of a plasticizer for thepurpose of reducing adhesiveness. Japanese Laid-Open Patent PublicationNo. 121016/77 states that the bond strength between this interlayer filmand a glass sheet is, for example, 4 to 10 pummel units. However, theinterlayer film of laminated safety glass shown in FIG. 3 of thisJapanese Laid-Open Patent Publication lacks penetration resistance. Whenthe content of glycidyl methacrylate in the copolymer of this Japanesepatent document is varied, the bond strength of the film can be improvedto some degree, but its penetration resistance can scarcely be improved.Furthermore, even if for the same purpose the flexibility of the filmitself is increased by increasing the amount of the plasticizer. Itsmechanical strength is reduced and sufficient penetration resistancecannot be obtained. Furthermore, if a large amount of the plasticizer isadded, it will bleed out in the space between the interlayer film andthe glass sheet, and may lead to a reduction in bond strength onlong-term use.

In view of the defects of conventional interlayer films of laminatedsafety glasses, the present inventors made extensive investigationsabout a resin composition containing a vinyl chloride resin which hasversatile application. These investigations have led to a novelcomposition for use as an interlayer film of a laminated safety glass,which has superior penetration resistance required of a laminate andexcellent bond strength and handleability in bonding.

SUMMARY OF THE INVENTION

According to this invention, there is provided a composition for aninterlayer film of a laminated safety glass, comprising (A) athermoplastic resin resulting from copolymerization of (1) vinylchloride, (2) glycidyl methacrylate and (3) at least one monomerselected from the group consisting of ethylenic hydrocarbons, vinylesters of fatty acids, acrylic esters, and vinyl ethers, and (B) aplasticizer.

DETAILED DESCRIPTION OF THE INVENTION

The thermoplastic resin used in this invention is a three-componentcopolymer comprising the components (1), (2) and (3) specified above.The suitable content of the glycidyl methacrylate (component 2) in thethree-component copolymer used in this invention is 1 to 10% by weight.If the content of the component (2) is less than 1% by weight, theresulting interlayer film has insufficient adhesion to a glass sheet. Ifits content exceeds 10% by weight, the resulting interlayer film hasreduced heat stability and undesirably undergoes coloration when bondedto a glass sheet.

The suitable content of the component (3), which is at least one monomerselected from ethylenic hydrocarbons, vinyl esters of fatty acids,acrylic esters and vinyl ethers, is at least 0.5% by weight, preferablynot exceeding 10% by weight. When a copolymer contains less than 0.5% byweight of the monomer (3), the resulting laminated safety glass hasinsufficient penetration resistance. If its amount exceeds 10%, theyield of the copolymer in copolymerization decreases, or the resultinginterlayer film has insufficient heat stability and undergoes colorationwhen bonded to a glass sheet.

The three-component copolymer may be produced by suspensionpolymerization, emulsion polymerization or solution polymerization. Fromthe standpoint of heat stability and economy, the suspensionpolymerization method is preferred. Suspending agents used in thesuspension polymerization may be any suspending agents generally used inpolymerization of vinyl chloride. When transparency is particularlyrequired in the interlayer film, polyvinyl pyrrolidone, partiallysaponified polyvinyl alcohol, polyvinyl methyl ether, methyl cellulose,etc. are used as suspending agents. Usually, all the monomers used inthe polymerization are charged together at the beginning of thepolymerization. However, it may be possible to add them portionwiseduring the polymerization. Preferably, the three-component copolymerused in this invention has an average degree of polymerization of atleast 500. If a copolymer having a higher degree of polymerization isused, better penetration resistance can be obtained.

Examples of the ethylenic hydrocarbons used as component (3) in thisinvention include ethylene, propylene and isobutylene. Examples of thevinyl esters of fatty acids are vinyl acetate, vinyl caproate, vinylpelargonate, vinyl laurate, vinyl myristate, and vinyl palmitate. Theacrylic esters include, for example, 2-ethylhexyl acrylate, methylacrylate, ethyl acrylate and 2-hydroxyethyl acrylate.

In forming the three-component copolymer used in this invention into afilm, suitable amounts of stabilizers, lubricants, ultravioletabsorbers, antioxidants, fillers, and coloring agents may beincorporated depending upon end uses. Stabilizers for polyvinyl chloridecan be widely used as the stabilizers. For example, metal soaps andorganotin compounds can be used. The suitable amount of the stabilizersis 1 to 10 parts by weight per 100 parts by weight of the thermoplasticresin.

In forming the three-component copolymer used in this invention into afilm, various plasticizers are incorporated. Those generally used asplasticizers for polyvinyl chloride can be widely used as suchplasticizers. Examples include esters of phthalic acid, adipic acid andsebacic acid, epoxy derivatives and polyester derivatives. Specificexamples are phthalates such as dioctyl phthalate, dibutyl phthalate anddiisobutyl phthalate; adipates such as di-2-ethylhexyl adipate anddiisodecyl adipate; and epoxy derivatives such as epoxidized soybean oiland monoesters of epoxy-fatty acids. The suitable amount of theplasticizer in the interlayer composition of this invention is 10 to 40%by weight. If it exceeds 40% by weight, the mechanical strength of theinterlayer film decreases markedly, and good penetration resistancecannot be obtained.

The interlayer composition of this invention can be made into a film byknown methods such as a calender roll method, an extrusion sheet castingmethod or an inflation method. A laminated safety glass can be producedby sandwiching the resulting film as an interlayer between glass sheets,and bonding the assembly under heat and pressure. Usually, the suitableheating temperature is 80° to 200° C., preferably 100° to 180° C. Thepressure may be one required for close adhesion between the glass sheetsand the interlayer and removal of air bubbles on the interface and inthe interlayer, and is suitably 5 to 15 kg/cm². In bonding the assemblyunder heat and pressure, there can be used bonding devices usedconventionally for bonding a plasticized polyvinyl butyral film, such asa hot press former, a press roll equipped with a heating oven, or ahydraulic or pneumatic pressure autoclave.

Since the composition of this invention for an interlayer film of alaminated safety glass has the aforesaid structure, it can be providedat low cost. When the composition is formed into a film for use as aninterlayer, it does not show tackiness by itself or to the glasssurfaces at room temperature. Hence, no antiblocking agent is necessary,and the step of bonding the interlayer film to glass sheets can beshortened. On the other hand, the bond strength between the interlayerfilm and the glass is sufficiently high, and the penetration resistanceof a laminated safety glass including the film of the composition ofthis invention as an interlayer is much higher than a laminated safetyglass including a conventional polyvinyl chloride resin film as aninterlayer.

The following Examples and Comparative Examples illustrate the presentinvention more specifically.

The tensile shear bond strength, 180° peel strength and penetrationresistance of each of the laminated safety glasses in these exampleswere measured by the following methods.

1. Tensile Shear Bond Strength

A laminate composed of a degreased glass sheet having a width of 25 mm,a length of 15 mm and a thickness of 5 mm, and a degreased steel sheethaving a width of 25 mm, a length of 100 mm and a thickness of 0.3 mm,and a resin sheet having a thickness of 1.5 mm interposed between them,the resin sheet being obtained by kneading on a two-roll mill, was setin a press machine heated at 160° C. It was preheated for 4 minutes,pressed at 3 kg/cm² for 4 minutes, and then cooled to prepare a testpiece. The resin protruding from the ends of the test piece was cut offby a knife, and the test piece was examined for tensile shear bondstrength by a tensile tester at a tensile speed of 200 mm/min. Themeasured value was converted to one per unit bonded area.

2. 180° Peel Strength

A resin sheet having a thickness of 1.5 mm obtained by kneading on atwo-roll mill and cut to a width of 30 mm and a length of 60 mm waslaminated to a degreased sheet glass having a width of 25 mm, a lengthof 50 mm and a thickness of 1 mm, and they were bonded under the sameconditions as described above for the tensile shear bond strength. Theedge portion of the laminate was trimmed by a knife. One end of theresin sheet was peeled, and bent in a 180° direction. Both ends of theresin sheet were held by a tensile tester and peeled off at a rate of200 mm/min. The strength value obtained was converted into a strengthvalue per unit width of the bonded portion.

3. Penetration Resistance

A resin sheet having a thickness of 1.5 mm was allowed to stand for oneday in a room kept at a temperature of 30° C. and a relative humidity is20%, and then interposed between two glass sheets having a size of 30.5cm×30.5 cm with a thickness of 2 mm to form a laminate. The laminate waspreheated at 70° C. for 10 minutes, and passed between rubber rollershaving a surface temperature of 70° to 75° C. to pre-press it at aplanar pressure of 3 kg/cm². The laminate was then put into a pneumaticpressure-type autoclave, heated to 150° C. over the course of 20minutes, and heated at this temperature for 20 minutes under a pneumaticpressure of 13 kg/cm². The heated laminate was then cooled to form atransparent laminated safety glass having a size of 30.5 cm×30.5 cm. Aplurality of such safety glass samples were each placed on a squareframe with one side measuring 30 cm, and at room temperature, a steelball weighing 5 pounds was let fall onto the center of the safety glassfrom varying heights. When 50% of the steel balls penetrated through thesafety glass samples, the height of the fall at this time was determinedand defined as the penetration resistance.

EXAMPLE 1

A 20-liter stainless steel autoclave was charged with 9.9 liters ofdeionized water, 34 g of methyl cellulose, 112 g of glycidylmethacrylate, 11.4 g of di-2-ethylhexyl peroxydicarbonate and 5.7 g ofsodium hydrogen carbonate, and the inside of the autoclave was placedunder a vacuum by a vacuum pump. Vinyl chloride monomer (5.5 kg) andthen 84 g of ethylene were fed into the autoclave. The polymerizationwas performed at 61° C. for 5 hours. The product was dehydrated, andanalyzed. It was found to contain 0.9% by weight of ethylene and 2.4% byweight of glycidyl methacrylate and have an average degree ofpolymerization of 770. Two hundred grams of the product, 6 g ofdibutyltin maleate and 80 g of di-2-ethylhexyl phthalate were put into abeaker, and were mixed well. The mixture was transferred to a two-rollmill heated at 160° C., and kneaded for 4 minutes to form a transparentflexible nontacky sheet having a thickness of 1.5 mm. The resin sheetwas interposed between two glass sheets, preheated for 4 minutes in apress machine at 160° C., and bonded for 4 minutes at a pressure of 3kg/cm². The resulting laminate was transparent.

The laminated safety glass obtained had a tensile shear bond strength of41 kg/cm², a 180° peel strength of 1.2 kg/cm and a penetrationresistance of 4.5 meters.

EXAMPLE 2

A copolymer containing 7.4% by weight of ethylene and 2.5% by weight ofglycidyl methacrylate and having an average degree of polymerization of910 was produced under the same conditions as in Example 1 except thatthe polymerization was performed at 50° C. for 8.5 hours using 11.2liters of deionized water, 36.8 g of methyl cellulose, 24.5 g ofglycidyl methacrylate, 24.5 g of di-2-ethylhexyl peroxydicarbonate, and6.1 g of sodium hydrogen carbonate, 5 kg of vinyl chloride monomer and 1kg of ethylene.

Using the resulting copolymer, a laminated safety glass was producedunder the same conditions as in Example 1. It was found to have apenetration resistance of 5.4 meters, a tensile shear bond strength of65 kg/cm², and a 180° peel strength of 2 kg/cm.

EXAMPLE 3

A copolymer containing 4.6% by weight of ethylene and 2.5% by weight ofglycidyl methacrylate and having an average degree of polymerization of680 was produced under the same conditions as in Example 1 except thatthe polymerization was performed at 60° C. for 8.5 hours using 76.5liters of deionized water, 214 g of methyl cellulose, 850 g of glycidylmethacrylate, 113 g of di-2-ethylhexyl peroxydicarbonate, 43 g of sodiumhydrogen carbonate, 37 kg of vinyl chloride monomer and 5.5 kg ofethylene in a 160-liter stainless steel autoclave.

Using the resulting copolymer, a laminated glass safety glass wasproduced under the same conditions as in Example 1. The resulting safetyglass had a penetration resistance of 4.8 meters, a tensile shear bondstrength of 57 kg/cm², and a 180° peel strength of 1.7 kg/cm.

EXAMPLE 4

A 20-liter stainless steel autoclave was charged with 11.8 liters ofdeionized water, 26 g of partially saponified polyvinyl alcohol, 210 gof vinyl acetate, 130 g of glycidyl methacrylate, 13 g ofdi-2-ethylhexyl peroxydicarbonate and 6.5 g of sodium hydrogencarbonate, and the inside of the autoclave was placed under a vacuum bya vacuum pump. Then, 6.2 kg of vinyl chloride monomer was fed into theautoclave. The polymerization was performed at 64° C. for 7 hours toafford a copolymer containing 2.9% by weight of vinyl acetate and 1.8%by weight of glycidyl methacrylate and having an average degree ofpolymerization of 650.

Using the resulting copolymer, a laminated safety glass was producedunder the same conditions as in Example 1. It was found to have apenetration resistance of 4.5 meters, a tensile shear bond strength of42 kg/cm² and a 180° peel strength of 1.85 kg/cm.

EXAMPLE 5

A 20-liter stainless steel autoclave was charged with 11.7 liters ofdeionized water, 39 g of methyl cellulose, 130 g of glycidylmethacrylate, 25 g of di-2-ethylhexyl peroxydicarbonate and 6.5 g ofsodium hydrogen carbonate, and the inside of the autoclave was placedunder a vacuum by a vacuum pump. Vinyl chloride monomer (5.8 kg) andthen 540 g of propylene were fed into the autoclave. The polymerizationwas performed at 45° C. for 14 hours to afford a copolymer containing3.6% by weight of propylene and 2.4% by weight of glycidyl methacrylateand having an average degree of polymerization of 630.

Using the resulting copolymer, a laminated safety glass was producedunder the same conditions as in Example 1. It was found to have apenetration resistance of 4.8 meters, a tensile shear bond strength of54 kg/cm² and a 180° peel strength of 1.9 kg/cm.

EXAMPLE 6

A 20-liter stainless steel autoclave was charged with 11.2 liters ofdeionized water, 27 g of partially saponified polyvinyl alcohol, 132 gof glycidyl methacrylate, 40 g of di-2-ethylhexyl peroxydicarbonate and6.5 g of sodium hydrogen carbonate, and the inside of the autoclave wasplaced under a vacuum by a vacuum pump. Vinyl chloride monomer (5.7 kg)and then 830 g of ethylene were fed into the autoclave. Thepolymerization was performed at 40° C. for 13 hours to afford acopolymer containing 4.8% by weight of ethylene and 2.5% by weight ofglycidyl methacrylate and having an average degree of polymerization of1290.

Using the resulting copolymer, a laminated safety glass was producedunder the same conditions as in Example 1. It was found to have apenetration resistance of 6.0 meters, a tensile shear bond strength of60 kg/cm² and a 180° peel strength of 1.9 kg/cm.

EXAMPLE 7

Two resin sheets obtained in each of Examples 1 to 6 were laminated, andplaced under a load of 400 g/cm² in an atmosphere kept at a temperatureof 20° C. and a relative humidity of 50%. Forty-eight hours later, theadhesiveness between the sheets was examined. It was found that theseresin sheets do not particularly show tackiness.

COMPARATIVE EXAMPLE 1

A 20-liter stainless steel autoclave was charged with 9.9 liters ofdeionized water, 22.5 g of partially saponified polyvinyl alcohol, 126 gof glycidyl methacrylate, 8.5 g of di-2-ethylhexyl peroxydicarbonate and5.6 g of sodium hydrogen carbonate, and the inside of the autoclave wasplaced under a vacuum by a vacuum pump. Vinyl chloride monomer (5.5 kg)was then fed into the autoclave. The polymerization was performed for 8hours at 61° C. to afford a copolymer containing 3.4% by weight ofglycidyl methacrylate and an average degree of polymerization of 650.

Using the resulting copolymer, a laminated safety glass was producedunder the same conditions as in Example 1. It was found to have apenetration resistance of 2.3 meters, a tensile shear bond strength of35 kg/cm² and a 180° peel strength of 0.9 kg/cm.

COMPARATIVE EXAMPLE 2

The same polymerization as in Comparative Example 1 was performed exceptthat the amount of the diglycidyl methacrylate was changed to 387 g.There was obtained a copolymer containing 7.8% by weight of glycidylmethacrylate and having an average degree of polymerization of 820.

Using the resulting copolymer, a laminated safety glass was producedunder the same conditions as in Example 1. It was found to have apenetration resistance of 2.3 meters, a tensile shear bond strength of40 kg/cm² and a 180° peel strength of 1.0 kg/cm.

The test data obtained in Examples 1 to 6 and Comparative Examples 1 and2 are summarized in the Table below.

                                      TABLE                                       __________________________________________________________________________    Item              Average    Tensile                                              Content                                                                             Content of                                                                            degree of                                                                          Penetration                                                                         shear bond                                                                          180° peel                               of GMA**                                                                            component (3)                                                                         polymeri-                                                                          resistance                                                                          strength                                                                            strength                                   Run*                                                                              (wt. %)                                                                             (wt. %) zation                                                                             (m)   (kg/cm.sup.2)                                                                       (kg/cm)                                    __________________________________________________________________________    Ex. 1                                                                             2.4   Ethylene                                                                              770  4.5   41    1.2                                                  (0.9)                                                               Ex. 2                                                                             2.5   Ethylene                                                                              910  5.4   65    2.0                                                  (7.4)                                                               Ex. 3                                                                             2.5   Ethylene                                                                              680  4.8   57    1.7                                                  (4.6)                                                               Ex. 4                                                                             1.8   Vinyl acetate                                                                         650  4.5   42    1.85                                                 (2.9)                                                               Ex. 5                                                                             2.4   Propylene                                                                             630  4.8   54    1.9                                                  (3.6)                                                               Ex. 6                                                                             2.5   Ethylene                                                                              1290 6.0   60    1.9                                                  (4.8)                                                               CEx. 1                                                                            3.4   None    650  2.3   35    0.9                                        CEx. 2                                                                            7.8   None    850  2.3   40    1.0                                        __________________________________________________________________________     *Ex. stands for Example, and CEx., for Comparative Example.                   **GMA stands for glycidyl methacrylate.                                  

What we claim is:
 1. In a laminated safety glass comprising two glasssheets bonded by an interlayer, the improvement wherein said interlayercomprises (A) a thermoplastic resin resulting from copolymerization of(1) 80 to 98.5% by weight of vinyl chloride, (2) 1 to 10% by weight ofglycidyl methacrylate and (3) 0.5 to 10% by weight of ethylene, and (B)10 to 40% by weight of a plasticizer.